1. Field
The present disclosure relates generally to communication systems, and more particularly, to wireless communication using a user equipment.
2. Background
Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., wireless spectrum, bandwidth, transmit power). Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.
These multiple access technologies have been adopted in various telecommunication standards to provide common protocols that enable different wireless devices to communicate on a municipal, national, regional, and even global level. An example of a recent telecommunication standard is Long Term Evolution (LTE). LTE is an evolvement of the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by the Third Generation Partnership Project (3GPP). Another approach in telecommunication is a circuit-switched (CS) network. Examples of wireless solutions supporting CS networks include Wideband CDMA (WCDMA), Global System for Mobile Communication (GSM) and CDMA2000. WCDMA and GSM are both defined by 3GPP whereas CDMA2000 is defined by the Third Generation Partnership Project 2 (3GPP2) all in publicly available documents. Various types of communications may be made using an LTE or a circuit-switched network, such as an emergency call. The emergency call notifies the network that the emergency call is a special type of call and may provide additional information (e.g. in the form of dialed digits or other call parameters) regarding special forms of call treatments such as routing to a particular Public Safety Access Point (PSAP) or providing a geographic location estimate for a calling user to a recipient PSAP. There is a need to place the emergency call in different types of networks because some networks may not support the emergency call while other networks do. Therefore, there is a demand for a convenient approach to initiate the emergency call in a network that can support the emergency call and to reinitiate an emergency call in such a network if an initially chosen network is not able to support the emergency call.